Thermal profiling for parallel on-line monitoring of biomass growth in miniature stirred bioreactors

Streamlining workflow and automation to accelerate laboratory scale protein production

Protein production facilities are often required to produce diverse arrays of proteins for demanding methodologies including crystallography, NMR, ITC and other reagent intensive techniques. It is common for these teams to find themselves a bottleneck in the pipeline of ambitious projects. This pressure to deliver has resulted in the evolution of many novel methods to increase capacity and throughput at all stages in the pipeline for generation of recombinant proteins. This review aims to describe current and emerging options to accelerate the success of protein production in Escherichia coli. We emphasize technologies that have been evaluated and implemented in our laboratory, including innovative molecular biology and expression vectors, small-scale expression screening strategies and the automation of parallel and multidimensional chromatography.

Scale-down simulators for metabolic analysis of large-scale bioprocesses

Analytical approaches for a comprehensive understanding of the metabolic networks in microbial cultures are mostly based on small-scale cultures which are in a steady state or undergo dynamic changes. For drawing conclusions to industrial-scale bioprocesses, however, it is important to understand that cells in large-scale bioreactors are exposed steadily to fast changes, because of an inhomogeneous environment. Analytical approaches that aim for large-scale bioprocess understanding need to apply specific laboratory simulators. Recent developments in cell cultivation techniques and computational tools provide improved possibilities to evaluate how a process will behave in the final scale. These simulators will pave the way for screening robust strains and process conditions.

Altering the ribosomal subunit ratio in yeast maximizes recombinant protein yield

Background

The production of high yields of recombinant proteins is an enduring bottleneck in the post-genomic sciences that has yet to be addressed in a truly rational manner. Typically eukaryotic protein production experiments have relied on varying expression construct cassettes such as promoters and tags, or culture process parameters such as pH, temperature and aeration to enhance yields. These approaches require repeated rounds of trial-and-error optimization and cannot provide a mechanistic insight into the biology of recombinant protein production. We published an early transcriptome analysis that identified genes implicated in successful membrane protein production experiments in yeast. While there has been a subsequent explosion in such analyses in a range of production organisms, no one has yet exploited the genes identified. The aim of this study was to use the results of our previous comparative transcriptome analysis to engineer improved yeast strains and thereby gain an understanding of the mechanisms involved in high-yielding protein production hosts.

Results

We show that tuning BMS1 transcript levels in a doxycycline-dependent manner resulted in optimized yields of functional membrane and soluble protein targets. Online flow microcalorimetry demonstrated that there had been a substantial metabolic change to cells cultured under high-yielding conditions, and in particular that high yielding cells were more metabolically efficient. Polysome profiling showed that the key molecular event contributing to this metabolically efficient, high-yielding phenotype is a perturbation of the ratio of 60S to 40S ribosomal subunits from approximately 1:1 to 2:1, and correspondingly of 25S:18S ratios from 2:1 to 3:1. This result is consistent with the role of the gene product of BMS1 in ribosome biogenesis.

Conclusion

This work demonstrates the power of a rational approach to recombinant protein production by using the results of transcriptome analysis to engineer improved strains, thereby revealing the underlying biological events involved.